Australian Plants Society NORTH SHORE GROUP
Ku-ring-gai Wildflower Garden
Topic 8: Ferns - Notes
FERNS
Did you know that,




Ferns appeared in the fossil record over 300 million years ago.
There are far fewer kinds of ferns than later evolving plants.
There are over 400 species of ferns in Australia and over 10,000
species worldwide.
In Australia, ferns occur mostly along the east coast.
Habitat
As ferns need water to reproduce, they are mostly found in rainforest or other moist
environments, like creek beds. However, there are some that grow in drier situations
and some that are drought resistant. An example of this is Cheilanthes, a type of
Resurrection Fern, as it will green up and stand erect after rain although it appeared to
be dead. There is even a fern which grows in mallee sand hills, another in sub-alpine
crevices which can be snow covered, and one in salt-sprayed crevices on the coast.
Growth
Ferns can be terrestrials, rooting on the ground; they can be lianas or creepers;
epiphytes living on the plants but feeding from airborne moisture and compost caught in
their structures; lithophytes, living in a similar manner to epiphytes but on rock; or in
water.
They range in size from tree-like structures, 20m tall, to tiny flimsy ferns only one cell
layer thick. The latter are subject to drying out so they can only live in very humid
atmospheres.
Growth of a frond is at the apex. The young leaves are rolled in tight spirals, unwinding
as they mature.
Structure
Like all higher plants, ferns are tracheophytes, i.e. they have vascular bundles to carry
water and nutrients, sap, through them.
They are like most plants in that they consist of a stem, called a rhizome, from which
roots grow into the soil, and leaves are held up. The leaves are green and carry on
photosynthesis.
Rhizome – is the stem of the fern plant. It can be vertical, as in the tree-fern. It is held
up by a strong girdle of sclerenchyma in association with the leaf bases and densely
matted aerial roots. Most rhizomes are prostrate, so the plant is spread along the
ground. In moist tropical areas the rhizome may run over the ground, but in drier areas
the rhizome grows under the ground, as it does with Bracken Fern.
The rhizome can be long–creeping, so fronds arise at a distance from one another, like
Bracken, or they can be short-creeping, producing a tufted fern like Blechnum species.
1
Pyrrosia rupestris
Sticherus flabellatus
Gleichenia rupestris
2
Frond – is the leaf. It may be only a few centimetres long, as in filmy ferns or it may be
several metres long, as in the Tree-fern.
The leaf blade can take various forms. It can be strap-like, simple, as in the Bird’s Nest
Fern. It can be once-divided, pinnate, as in Blechnum sp or Lindsaea linearis. It can be
twice-divided, bipinnate, or thrice-divided, tripinnate, as in Cheilanthes sieberi.
Asplenium australasicum
Lindsaea linearis
Cheilanthes sieberi
Sori (plural of sorus) – are arranged in many ways on the undersides of the fronds.
These patterns are used by taxonomists to classify and identify ferns. See next page.
Sori may be: in a line along the lateral veins (Asplenium australasicum); in a line along
either side of a pinna central vein (Blechnum); in rows midway between pinnule midvein and leaf margin (Cyathea cooperi); along the pinnule margin (Dicksonia antarctica –
in this species the leaf margin is rolled well over the sorus to meet in an indusium);
along the upper leaf margin which is slightly rolled over the elongated sorus (Adiantum
formosum).
Indusium – is a thin outgrowth from the frond that grows partly over the sorus to
protect it. They come in many shapes. Some sori are naked, called exindusiate. A false
indusium is formed by the leaf margin curving over the sorus.
3
Dimorphism – is the condition where the fertile frond, bearing sori on the undersurface of the frond, is noticeably different in form from the sterile frond. Examples of
this are Doodia caudata, Blechnum cartilagineum.
4
Reproduction
Ferns can reproduce either sexually or asexually. Sexual reproduction is described in the
following diagram.
FERN LIFE CYCLE
Asexual reproduction is by the rhizome between fronds dying, separating them. Some
ferns produce small plants by budding on the frond, as in Polystichum proliferum, and
Asplenium bulbiferum (Mother Spleenwort).
5
Fern Allies
Fern allies are ancient plants, like ferns. They are termed “fern allies” because they coexisted with ferns in the early years of the evolution of plant life on land, and also
reproduced by spores, not seeds. Many of the current species, in Lycopodiaceae and
Selaginellaceae, had already taken a different evolutionary path from the true ferns, and
athough they flourished during the Late Devonian and Carboniferous eras very few have
made it through to modern times.
One of the oldest plants of all, predating the true ferns by about 75 million years, is
Rhynia. It is very similar to the skeleton fork fern or Psilotum nudum which occurs
along coastal districts all around Australia and the western Pacific. It has changed little
in 400 million years. It consists of a rhizome which absorbs nutrients by rhizoidal hairs
in association with mycorrhizal fungi. The forking rhizomes and the stems bear small
scale or leaf like appendages. The stems bear stomata and are photosynthetic. Thickwalled yellow sporangia are borne at the end of short side branches. It can be found
growing out of crevices in Hawkesbury Sandstone cliffs, occurring locally on the Mueller
Track in the Wildflower Garden, North Epping, Mt Colah and Berrilee.
The Lycopods developed internal structures which enabled them to grow into trees of up
to 45m. During the late Devonian and Carboniferous ages they dominated many parts
of the world with dense forests. Surviving members are small herbs, some of which can
be found in Sydney bushland. Lycopods, like ferns and Psilotum, also have horizontal
rhizomes, root hairs or rhizoids, and aerial stems.
Three species can be found in the northern suburbs - Lycopodium deuterodensum,
Lycopodiella lateralis and Lycopodiella cernua. They do not produce fronds but have
stems bearing simple, single-veined small leaves. Spores are borne in terminal club-like
cones, called “strobili”.
Lycopodium deuterodensum bears two types of aerial stems, sterile and fertile, with
different leaves. Leaves on the sterile stems are about 3mm long and spreading. Those
on the fertile stems are about 2mm long and appressed.
Lycopodiella species have only one type of aerial stem with spreading leaves and
terminal strobili. In all three Lycopods the strobili are similar - the leaves, sporophylls,
are crowded, with sporangia attached to their bases. Spores of only one kind are
produced.
Selaginella is represented in Sydney by one native species, Selaginella uliginosa, and
one introduced species, S. kraussiana. They are similar to Lycopods in many ways, but
they have sporangia of two types, producing spores of two types.
All fern allies, like the ferns, produce alternating sporophyte and gametophyte
generations. The gametophyte generation, the prothallus, is tiny, producing sex cells,
the union of which produces the sporophyte generation which are described above.
6
Evolution of Ferns and Fern Allies
7
Ferns and Fern Allies found in the Ku-ring-gai Wildflower Garden
Adiantum aethiopicum
Adiantum hispidulum
Adiantum silvaticum
Asplenium australasicum
Asplenium flabellifolium
Azolla pinnata
Blechnum cartilagineum
Blechnum minus
Blechnum nudum
Calochlaena dubia
Cheilanthes sieberi
Christella dentata
Cyathea australis
Cyathea cooperi
Davallia solida var. pyxidata
Dennstaedtia davallioides
Deparia petersenii subsp. congrua
Dicksonia antarctica
Dictymia brownii
Doodia aspera
Doodia caudata
Gleichenia dicarpa
Gleichenia microphylla
Gleichenia rupestris
Grammitis billardierei
Grammitis stenophylla
Histiopteris incisa
Hymenophyllum cupressiforme
Hypolepis muelleri
Lindsaea linearis
Lindsaea microphylla
Lycopodiella cernua
Marsilea sp
Microsorum scandens
Platycerium bifurcatum
Polystichum proliferum
Psilotum nudum
Pteridium esculentum
Pteris vittata
Pyrrosia confluens
Pyrrosia rupestris
Schizaea bifida
Schizaea dichotoma
Selaginella kraussiana*
Sticherus flabellatus
Todea barbara
Common Maidenhair Fern
Rough Maidenhair Fern
Forest Maidenhair Fern
Bird’s Nest Fern
Necklace Fern
Azolla
Gristle Fern
Soft Water Fern
Fishbone Water Fern
Rainbow Fern
Rock Fern
Binung, Binung
Rough Tree Fern
Straw Tree Fern
Hare’s Foot Fern
Lacy Ground Fern
Japanese Lady Fern
Soft Tree Fern
Strap Fern
Rasp Fern
Small Rasp Fern
Pouched Coral Fern
Scrambling Coral Fern
Coral Fern
Finger Fern
Finger fern
Bat’s Wing Fern
Common Filmy Fern
Harsh Ground Fern
Screw Fern
Lacy Wedge Fern
Scrambling Clubmoss (Fern Ally)
Nardoo
Fragrant Fern
Elkhorn Fern
Mother Shield Fern
Skeleton Fork-Fern (Fern Ally)
Common Bracken
Chinese Brake
Robber Fern
Rock Felt Fern
Forked Comb Fern
Branched Comb Fern
Spreading Clubmoss (Fern Ally, *non-native)
Umbrella Fern
King Fern
Acknowledgements: Jones, DL & Clemesha, SC Australian Ferns and Fern Allies,
1981. Beadle, N. Flora of the Sydney Region, 1962.
These notes contain hyperlinks to materials, including images, illustrations, plant
descriptions and a glossary from PlantNET, with the courtesy of The Royal Botanic
Gardens & Domain Trust, 2011.
For general access to PlantNET see also http://plantnet.rbgsyd.nsw.gov.au/
Produced by North Shore Group, Australian Plants Society. Revised: JL, WG 2011.
8